The science and art of paleontology
A blog on dinosaur anatomy and reconstructing the appearance of prehistoric animals.
The Super Spinosaurus? post produced some interesting conversation; in particular Marco asked a good question about whether using the skull of the South American spinosaurid Irritator would have a material impact on the size of the animal. Let's take a quick look at Irritator's skull, and then a broader look at how these sorts of questions do (or don't) impact mass estimates.
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In the past I have been skeptical of claims of 50+ foot Spinosaurus specimens - and with how little we know about the tail length in Spinosaurus there is still reason for caution.
That said, science is always based on data, and sometimes the data isn't what you expected. I was reminded of this once again recently after I tweaked the scaling of elements in my Spinosaurus skeletal reconstruction. The "main" skeletal seen above (the fully restored version is in the theropod gallery) is based on a composite skeletal of the type specimen and other various referred bits. Previously I'd had the mandible scaled up too much by about 6%. After correcting I measured and sure enough, a nice 14m (46 foot) long beast.
Now please use some caution here: as you can see the composite skeletal is missing large swaths of bones. I have filled those in with bones from other relatives (e.g. Baryonyx and Suchomimus), but there's definitely some uncertainty here. Of particular note, tail length varies quite a bit in dinosaurs (as demonstrated recently by Dave Hone), and I would feel a lot better about estimating the length if we had some more Spinosaurus tail vertebrae.
Still, unless you restore an almost comically long tail the type specimen of Spinosaurus was less than 50 feet. Ah, but that's not the largest specimen! The biggest specimen referred to Spinosaurus is MSMN V4047, a giant snout that Dal Sasso et al described in 2005.
Assuming that the composite is scaled correctly and that the giant MSMN specimen scales up isometrically (which seems probable) then it would be in the range of 15.6 meters (51 feet) give or take. That's one long theropod we are looking at! Given our margin of error it's entirely possible that the MSMN specimen is actually 48 feet (or 55 feet!), but assuming it had proportions similar to that of other spinosaurids, then it seems clear that 50 foot lengths were most likely attained.
Of course length is just one estimate of size, and mass is generally considered more important. And here things get interesting. Check back this weekend for a closer look at how much Spinosaurus may have tipped the scales in life.
I'm often asked about what I think of "transitional fossils". Here's the thing: it's a red herring. Not because we can't see important transitions everywhere in the fossil record, but because a single fossil can't show a transition by definition. If you want to see a transition you need a series of related animals, generally organized by who is related to whom.
Read MoreToday let's look at another one of our thundering giants, Alamosaurus sanjuanensis. Alamosaurus is known from quite good remains (for a titanosaur), and some fragmentary remains may be close to the largest known dinosaur. How certain is this reconstruction? Much better than Puertasaurus, but there are still a couple of layers of inference needed to get there.
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Puertasaurus reuili
When I released my Thunder Lizards size comparison I was asked why a few of the largest animals were rendered in gray, and when I would be making the actual skeletal available. Using gray silhouettes solved an aesthetic concern (the image was threatening to get too busy), but it turns out that those critters have another problem: they are not known from very incomplete remains.
So here is the skeletal of Puertasaurus in all its "glory". I have a fully restored version as well, but it's not going to be making a public appearance, as frankly I don't want it to be separated from the rigorous version, as that could give off the impression that the animal is better known. In fact even this version is somewhat misleading, as the two tail vertebrae were reported but not figured or described - I don't actually know how big they were!
That's not to say the reconstruction is a fantasy - it's status as a lognkosaur seems secure, and we have very good remains of some of its relatives. And the neck and back vertebrae actually provide a pretty reasonable basis for scaling the largest parts of Puertasaurus. That said, I feel it's important for scientists (and scientific illustrators) not to inadvertently mislead people about the level of inference involved.
So enjoy the skeletal, but please do so responsibly!
If this isn't your first time to my website, you're probably noticing that things look quite a bit different around here. That's because after numerous fits and false starts, I finally got around to redesigning the site. I think the site is now quite a bit more attractive, but more importantly it is using modern web technology.
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I don't know if that grabs your attention, but sorting out the size of giant sauropods sure grabs mine. Let's take a more detailed look at some of the critters in this image:
First off, I need to admit that this is not all inclusive. The legendary Amphicoelias fragillimus will never be included (unless more material is found). I have not sufficiently nailed down the scaling of Argentinosaurus yet to include it, but early scaling makes it look like it's the same size or slightly smaller than Puertasaurus (which I did include).
Note that most of these animals are only known from a single specimen (and often quite incomplete skeletons at that), which means that we don't really know what the size range of animals was in a living population. So keep in mind that while we can compare individual specimens, we can't say with any certainty that the biggest skeleton really came from the biggest sauropod species.
Here are some other quick hits:
1) For personal reasons I love me some Supersaurus. I've scaled the reconstruction to the size of the WDC specimen (32m), though the type specimen may have reached 34m in length. Either way it's the longest sauropod we can reasonably restore, though it certainly was not the heaviest (diplodocids tend to be fairly slab-sided compared to titanosaurs).
2) The large NMMNH Diplodocus specimen (originally named Seismosaurus) is also very long (~30m) but probably even lighter in mass.
3) Diplodocids may rule the roost in length, but macronarians seems to (mostly) crush them in terms of mass. Puertasaurus is currently my reigning champion; filling in the (extensive) missing elements with other lognkosaur relatives leads to a 27 meter long animal that is clearly the heaviest of the group (I'll speculate maybe in the 60-70 tonne range, but treat that as arm waving until it's verified by volumetric or double integration analysis).
4) To elaborate on preliminary Argentinosaurus results (not included above), it’s in the same size range as Puertasaurus, but basal titanosaurs may have had somewhat shorter tails (hence the smaller length) and the vertebrae aren't quite as wide as Puertasaurus, so my best guesstimate is that it loses on both accounts to it's lognkosaur relative, if only by a weeeee bit.
5) I didn't include Paralititan but I did scale it (hey, there's only so much space). It's large, but appears to be somewhat smaller than the Dallas specimen of Alamosaurus.
6) Speaking of Alamosaurus, I spent a lot of time trying to sort out who had the biggest fragmentary remains between Fowler & Sullivan (2010) and Guzman-Gutierrez & Palomino-Sanchez (2006). The tibia from Mexico is easily biggest (see gray silhouette behind the main Alamosaurus), but foreground skeletal here is based on Fowler and Sullivan's largest specimen (an isolated tail vertebrae) which happens to be from animal almost exactly the same size as the specimen on display at the Perot Museum of Nature and Science. Of course at this point we don't know for sure if the mexican tibia is truly Alamosaurus, or something new.
6) Brachiosaurus has long been abandoned in discussions of who is the largest dinosaur, but I'm not sure that's a good idea. The skeletal above is restored to the size of the type specimen, but some of the Utah specimens may be larger. The very broad-gutted Puertasaurus ekes out a larger size, but with such small sample sizes I don't think Brachiosaurus can actually be ruled out at the species level.
7) On the other hand, the significantly less robust Giraffatitan probably can be ruled out despite being quite tall.
8) While titanosaurs are generally heavier than diplodocids, very large Apatosaurus specimens appear to fit comfortably in the same size class. In addition to the Oklahoma specimen I have seen a few other (unpublished) apatosaur specimens that at least rival it in size.
So there you have it. If you have any other questions hit me up in the comments section below.
Paleontologist and paleoartist Scott Hartman provides a wealth of anatomical data and skeletal drawings of dinosaurs, and information on how prehistoric animals looked in life.
